package 二叉树;

public class BinaryTree {

    static class TreeNode {
        public char val;
        public TreeNode left;
        public TreeNode right;

        public TreeNode(char val) {
            this.val = val;
        }
    }

    /**
     * 创建一棵二叉树 创建成功后 返回根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        TreeNode G = new TreeNode('G');
        TreeNode H = new TreeNode('H');

        A.left = B;
        A.right = C;
        B.left = D;
        B.right = E;
        C.left = F;
        C.right = G;
        E.right = H;

        return A;
    }

    // 前序遍历
    void preOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        System.out.print(root.val + " ");
        preOrder(root.left);
        preOrder(root.right);
    }


    // 中序遍历  -》 左根右
    void inOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        preOrder(root.left);
        System.out.print(root.val + " ");
        preOrder(root.right);
    }

    // 后序遍历  -》 左右根
    void postOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        preOrder(root.left);
        preOrder(root.right);
        System.out.print(root.val + " ");
    }

    int size(TreeNode root){
        if (root == null){
            return 0;
        }
        return size(root.left)+size(root.right)+1;
    }

    // 获取叶子节点的个数
    int getLeafNodeCount(TreeNode root){
        if(root == null){
            return 0;
        }
        if(root.left == null&&root.right == null){
            return 1;
        }
        return getLeafNodeCount(root.left)+getLeafNodeCount(root.right);
    }

    // 获取第K层节点的个数
    int getKLevelNodeCount(TreeNode root,int k) {
        if(root == null){
            return 0;
        }
        if(k == 1){
            return 1;
        }
        return getKLevelNodeCount(root.left,k-1)+getKLevelNodeCount(root.right,k-1);
    }

    // 获取二叉树的高度
    int getHeight(TreeNode root) {
        if (root == null){
            return 0;
        }
        int leftheight = getHeight(root.left);
        int rightheight = getHeight(root.right);
        return leftheight>rightheight?leftheight+1:rightheight+1;
    }

    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if (root == null){
            return null;
        }
        if (root.val == val){
            return root;
        }
        if(root.right == null&&root.left == null){
            return null;
        }

        TreeNode ret = find(root.left,val);
        if (ret!=null){
            return find(root.left,val);
        }

        TreeNode ret2 = find(root.right,val);
        if(ret2!=null){
            return find(root.right,val);
        }

        return null;
    }
}
